diff --git a/scripts/ramdisk-orchestrator.sh b/scripts/ramdisk-orchestrator.sh
index 7bc07f91..fdcc628d 100755
--- a/scripts/ramdisk-orchestrator.sh
+++ b/scripts/ramdisk-orchestrator.sh
@@ -19,7 +19,9 @@
 #     --push              Push committed fixes to remotes
 #     --dry-run           Show what would be done without doing it
 #     --keep              Do not unmount RAM disk on completion
-#     --mount PATH        Custom mount point (default: per-user hypatia/workspace)
+#     --mount PATH        Custom mount point (default: hypatia/workspace under
+#                         $XDG_RUNTIME_DIR, else $XDG_STATE_HOME, else
+#                         ~/.local/state)
 #     --max-repos N       Limit number of repos to process
 #     --fallback-disk     Fall back to Eclipse drive if RAM is insufficient
 #     --quiet             Suppress non-essential output
@@ -43,8 +45,9 @@ FARM_DIR="${FARM_DIR:-${HYPATIA_DIR}/../.git-private-farm}"
 ECLIPSE_REPOS="${HYPATIA_REPOS_DIR:-$(dirname "$HYPATIA_DIR")}"
 
 # Defaults
-WORKSPACE_BASE="${XDG_RUNTIME_DIR:-${XDG_STATE_HOME:-$HOME/.local/state}}/hypatia"
-MOUNT_POINT="${WORKSPACE_BASE}/workspace"
+# Empty until parse_args has run: --help and --mount must work even when
+# neither XDG variable nor HOME is set. See resolve_mount_point.
+MOUNT_POINT=""
 RAMDISK_SIZE="2G"
 ORG="hyperpolymath"
 SEVERITY="high"
@@ -103,6 +106,23 @@ parse_args() {
     done
 }
 
+# The tmpfs mount point is re-found by later runs (stale-mount reuse), so it
+# lives in a per-user directory, not a mktemp one. With no XDG directory and
+# no HOME there is nowhere to put it: say so and stop, rather than let
+# `set -u` die on an unbound HOME before --help can run.
+resolve_mount_point() {
+    [[ -n "$MOUNT_POINT" ]] && return 0
+    local base="${XDG_RUNTIME_DIR:-${XDG_STATE_HOME:-}}"
+    if [[ -z "$base" && -n "${HOME:-}" ]]; then
+        base="$HOME/.local/state"
+    fi
+    if [[ -z "$base" ]]; then
+        log_err "No XDG_RUNTIME_DIR, XDG_STATE_HOME or HOME; pass --mount PATH"
+        exit 1
+    fi
+    MOUNT_POINT="$base/hypatia/workspace"
+}
+
 # ─────────────────────────────────────────────────────────────────────
 # Resource checks
 # ─────────────────────────────────────────────────────────────────────
@@ -177,7 +197,9 @@ mount_workspace() {
         if ! sudo -n true 2>/dev/null; then
             log_warn "No passwordless sudo — falling back to disk workspace"
             USE_TMPFS=false
-            MOUNT_POINT="${WORKSPACE_BASE}/workspace-$$"
+            # Scratch space: XDG_RUNTIME_DIR is itself a small tmpfs, so
+            # use the system temp dir, with an unpredictable name.
+            MOUNT_POINT="$(mktemp -d -t hypatia-workspace.XXXXXXXX)"
         fi
     fi
 
@@ -497,6 +519,7 @@ generate_summary() {
 # ─────────────────────────────────────────────────────────────────────
 main() {
     parse_args "$@"
+    resolve_mount_point
 
     log "${BOLD}Hypatia RAM Disk Orchestrator v${VERSION}${NC}"
 
diff --git a/tests/e2e.sh b/tests/e2e.sh
index f904e715..6c4d59f9 100644
--- a/tests/e2e.sh
+++ b/tests/e2e.sh
@@ -77,6 +77,17 @@ else
 fi
 echo ""
 
+# ─── RAM disk orchestrator mount resolution ────────────────────────
+bold "RAM disk orchestrator mount resolution"
+
+if ramdisk_output="$(bash "${PROJECT_DIR}/tests/ramdisk-orchestrator-test.sh" 2>&1)"; then
+    pass "ramdisk-orchestrator resolves its mount point after parsing and refuses to run without one"
+else
+    fail_test "ramdisk-orchestrator mount resolution"
+    printf '%s\n' "${ramdisk_output}"
+fi
+echo ""
+
 # ─── Create test fixture ────────────────────────────────────────────
 FIXTURE_DIR="$PROJECT_DIR/integration/fixtures/test-repo"
 if [ ! -d "$FIXTURE_DIR" ]; then
diff --git a/tests/ramdisk-orchestrator-test.sh b/tests/ramdisk-orchestrator-test.sh
new file mode 100755
index 00000000..91f34285
--- /dev/null
+++ b/tests/ramdisk-orchestrator-test.sh
@@ -0,0 +1,81 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: MPL-2.0
+# Mount-point resolution in scripts/ramdisk-orchestrator.sh: the default is
+# found after argument parsing, so --help and --mount work with no HOME and
+# no XDG directory, and a run with nowhere to mount says so and stops.
+# Every run is --dry-run with a repo name that exists nowhere: nothing is
+# cloned, mounted or scanned.
+set -euo pipefail
+
+repo_root="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+script="$repo_root/scripts/ramdisk-orchestrator.sh"
+fixture_root="$(mktemp -d /tmp/hypatia-ramdisk-test.XXXXXX)"
+# cleanup removes the temporary fixture directory when its path matches the expected safe pattern.
+cleanup() {
+  case "$fixture_root" in
+    /tmp/hypatia-ramdisk-test.*) rm -rf -- "$fixture_root" ;;
+    *) echo "refusing unsafe cleanup target: $fixture_root" >&2 ;;
+  esac
+}
+trap cleanup EXIT
+
+mkdir -p "$fixture_root/repos" "$fixture_root/run" "$fixture_root/state"
+failures=0
+
+# run_bare <env...> -- <args...>: the script in an environment holding only
+# PATH, the given variables, and an empty repos directory; output in $out,
+# status in $status.
+run_bare() {
+  local vars=()
+  while [[ "$1" != "--" ]]; do vars+=("$1"); shift; done
+  shift
+  status=0
+  out="$(env -i PATH="$PATH" HYPATIA_REPOS_DIR="$fixture_root/repos" "${vars[@]}" \
+    bash "$script" "$@" 2>&1)" || status=$?
+}
+
+check() {
+  local label="$1" ok="$2"
+  if [[ "$ok" == "true" ]]; then
+    echo "PASS: $label"
+  else
+    echo "FAIL: $label"
+    printf '  status %s, output:\n%s\n' "$status" "$out" | sed 's/^/  /'
+    failures=$((failures + 1))
+  fi
+}
+
+# --help needs no HOME.
+run_bare -- --help
+check "--help runs with no HOME or XDG directory" \
+  "$([[ "$status" -eq 0 && "$out" == *"--mount PATH"* ]] && echo true || echo false)"
+
+# Nowhere to mount: a clear refusal naming the way out, not an unbound HOME.
+run_bare -- --dry-run --size 1M no-such-repo
+check "no HOME or XDG directory: refused, naming --mount" \
+  "$([[ "$status" -eq 1 && "$out" == *"pass --mount PATH"* && "$out" != *"unbound variable"* ]] && echo true || echo false)"
+
+# --mount is enough on its own.
+run_bare -- --dry-run --size 1M --mount "$fixture_root/m" no-such-repo
+check "--mount with no HOME or XDG directory" \
+  "$([[ "$status" -eq 0 && "$out" == *"Would mount tmpfs (1M) at $fixture_root/m"* ]] && echo true || echo false)"
+
+# The default follows XDG_RUNTIME_DIR, then XDG_STATE_HOME, then HOME.
+run_bare XDG_RUNTIME_DIR="$fixture_root/run" XDG_STATE_HOME="$fixture_root/state" HOME="$fixture_root" -- \
+  --dry-run --size 1M no-such-repo
+check "default under XDG_RUNTIME_DIR" \
+  "$([[ "$status" -eq 0 && "$out" == *"at $fixture_root/run/hypatia/workspace"* ]] && echo true || echo false)"
+
+run_bare XDG_STATE_HOME="$fixture_root/state" HOME="$fixture_root" -- --dry-run --size 1M no-such-repo
+check "default under XDG_STATE_HOME" \
+  "$([[ "$status" -eq 0 && "$out" == *"at $fixture_root/state/hypatia/workspace"* ]] && echo true || echo false)"
+
+run_bare HOME="$fixture_root" -- --dry-run --size 1M no-such-repo
+check "default under HOME/.local/state" \
+  "$([[ "$status" -eq 0 && "$out" == *"at $fixture_root/.local/state/hypatia/workspace"* ]] && echo true || echo false)"
+
+if [[ "$failures" -gt 0 ]]; then
+  echo "ramdisk-orchestrator-test: $failures failure(s)"
+  exit 1
+fi
+echo "ramdisk-orchestrator-test: all passed"